JPH03104445A - Duplicate system for bus type network - Google Patents

Abstract

PURPOSE:To offer highly reliable network by providing MODEM sections in a data input and output section of each station in duplicate, connecting respective MODEMs to different 2 systems of transmission lines and switching only a relevant station to other system with respect to a local fault. CONSTITUTION:A head end remodulator 15 for main system transmission line connects to one end of a main system transmission line 10 and one terminal of an interlocking 2-way amplifier 5 connects to the other end of the main system transmission line 10. When a MODEM 11A of a station 3A is faulty, the station 3A selects a changeover switch 4A from the position of the MODEM 11A to the MODEM 21A. Thus, only the station 3A is selected to a standby system transmission line 20. The data transmission reception between the station 3A and other stations 3B, 3C is implemented via the interlocking 2-way amplifier 5 where the transmission lines are connected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a duplex system for bus-type networks, and particularly to a duplex system for broadband-type bus networks. [Prior Art] Conventionally, CSM A/CD (IEEE 802.
3) LAN or Tokoun bus (IEEE 802
．． 4) LAN, which uses coaxial cables and runs horizontally in the form of a bus, has been around for a long time.

These bus-type LANs have the characteristic that, like the ring-type LANs that have been used in Japan for a long time, even if the power to a node station is cut off, the entire system is not affected. However, the disadvantage is that when the transmission line is cut or when adding stations, the entire system may go down or the system must be stopped. On the other hand, in a ring-type LAN, the transmission path is duplicated and a loopback function is incorporated, so that even if one transmission path is disconnected, the system will not go down.

Therefore, even in bus-type networks, attempts have been made to make the transmission line and modem redundant so that the system can operate normally even if the transmission line is disconnected or the modem fails. FIG. 2 shows a duplex system in a broadband bus network. The modem 11^, II is connected to the main transmission line 10 and the protection transmission line 20 using a brancher 13.
B, 11C, modem 21A, 21B. 2 ICs are connected, and each station 3 A, 3 B, 3 C can be switched to the main transmission line 10 or the standby transmission line 20 using switchers 4 A, 4 B, 4 G. The main transmission line 10 and the standby transmission #I20 each have one end connected to a terminating resistor 12.
22, a head end remote generator 15.25 is provided at the @ end, and a bidirectional amplifier 14.2 is provided in the middle.
4 has been inserted.

During normal operation, stations 3A, 3B, 3C
The data output from one of the stations, for example, 3^, passes through the main modem 118 and is transmitted from the main transmission line 10 to different stations 3B and 3C, respectively.If a certain modem, for example, When the IIA fails, all stations simultaneously switch the switch 4^, 48.4C to the dotted line side and resume data transmission using the backup transmission line 20.

[Problems to be solved by the invention However, this method has the following problems. (1) Since the entire system is switched to the standby system even if one modem (11^) fails, stations 38. Even for 3C modems that are working properly,
We will have to switch to a backup system whose operation is not guaranteed,
This does not necessarily mean that reliability has increased. (2) If a modem or drop gear fails, it does not affect the information transmission of other stations, making it difficult for all stations to recognize this failure. If this recognition is not possible, switching to the standby system will not be possible. To avoid this situation, special information must be transmitted to confirm the operating status of each station. (3) Even if a transmission system were adopted to solve the problem (2) above, it would be difficult to distinguish between a station power outage and a modem failure. As a result, the greatest advantage of the bus-type network, which is the ability to turn on and off stations at Mt. Hakusan, is subject to some limitations. An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a highly reliable network that switches only abnormal parts as much as possible. [Means for Solving the Problems] The bus-type network redundancy system of the present invention is a broadband network in which branch sections are provided at multiple locations on a transmission line, stations are connected to each branch, and data is transmitted to each other via the transmission line. In a bus-type network, the modem section, which is the data input/output section of each station, is duplicated, each modem is connected to two different transmission lines, and the first head end remote modulator is connected to one end of one system. ,
The other end of the one system is switchably connected to the second headend remote modulator via a changeover switch to the other end of the other system whose one end is terminated with a terminating resistor, so that it can be connected to the second headend remote modulator in a manner that prevents local failure of the modem, etc. On the other hand, only the corresponding stations are switched to the other system.

In this case, it is preferable to provide a relay transmission device between the other end of the one system and the changeover switch.

[Operation] In the event of a minor failure, such as a failure of one modem, the transmission line can be switched to either that station alone or to a different transmission line.
Therefore, in both the first form and the second form,
Data can be transmitted from the backup transmission line to the main transmission line or vice versa, either directly or via relay transmission equipment other than the transmission line, such as a bidirectional amplifier. Only the modem at the abnormal location is switched, and the other stations are in the same state as when normal, so reliable data transmission is guaranteed as before the abnormality occurred. In addition, in the case of a serious failure such as a failure of the main transmission line or the head-end remote modulator for the main transmission line, a signal sensor etc. By switching to , it is possible to maintain information communication using only the backup transmission line.

[Example] Hereinafter, a specific example of the present invention will be described using FIG. 1. In FIG. 1, a main transmission line head entry modulator 15 is connected to the -@ (left side of the figure) of the main transmission line 10, and a linking head entry modulator 15 is connected to the other end of the main transmission line 10. One end of bidirectional amplifier 5 is connected. On the other hand, a termination resistor 22 equal to the characteristic impedance of the transmission line is connected to one end of the protection transmission line 20 (left side in the figure), and a changeover switch 7 is connected to the other end of the protection transmission line 20.
A standby system head entry modulator 25 is switchably connected to the linking bidirectional amplifier 5 via the linking bidirectional amplifier 5. In other words, the other end of the linkage bidirectional angler and the standby system head entry modulator 25 are connected to the standby system transmission line 20 via the changeover switch 7 so as to be switchable between the two. . This changeover switch 7 is selectively controlled by a downlink signal detector 6 provided at one end of the linkage bidirectional amplifier 5. Note that bidirectional amplifiers 14 and 24 are inserted between the main transmission line 10 and the protection transmission line 20. Main transmission line 1
0, using a plurality of switches 13 as in the conventional case,
Modem 1 of stations 3A, 3B, 3C
1A, 1 1B, 1 1C are connected, and the modem 2 of stations 3A, 3B, 3G is connected to the standby system transmission F#120 using a plurality of branchers 23.
1A, 2 1B, 2 ICs are connected. Stations 3 A and 3 B transmit and receive data.
, 3C can be connected to either of the above modems using switchers 4^, 4B, and 4C, respectively. First, under normal conditions, each station 3^, 3 B,
The switching devices 4^ and 48.4C of 3C are controlled for the main system measurement, and the linkage changeover switch 7 is controlled for the bidirectional amplifier side, and data is sent and received using only the main transmission line 10. It will happen. If the main modem 11^, 11B, II is being used
If a failure occurs in modem IIA of station 3^, for example, as shown by the X mark in FIG. 2, station 3A switches the switch 4A from modem 11^ measurement to modem 21^ music. As a result, only the station 3A is switched to the backup transmission line 20. Transmission and reception of data between the station 38 and the other stations 3B and 3C is performed via a linking bidirectional amplifier 5 that connects the transmission lines. Furthermore, in the event that the main transmission line 8@10 is disconnected, data transmission and reception on the main line becomes impossible due to signal reflection at the disconnection point, so all stations switch their modems to the standby line. At the same time, the downstream signal sensor 6 detects a failure when the downstream signal from the main system head entry modulator 15 is cut off, and switches the changeover switch 7 to the backup system head entry modulator 25. In this way, all devices are connected to the backup system, and data is sent and received using the backup transmission line 20. In this way, a bidirectional amplifier is installed between the main transmission line and the protection transmission line. By inserting a downstream signal sensor and a switching switch, in the event of a partial failure such as a failure of the modem at one station or an abnormality in the branch terminal of a switch, only the relevant part is switched to the standby system, and the system is switched on during normal operation. Since the Ike station is in the same state as normal, it is possible to guarantee reliable data transmission as before the abnormality occurred. Also, compared to the cost of a duplex system according to the prior art, the increase in cost is considered to be small because only one bidirectional amplifier, one switch, and one downstream signal sensor are added.

In addition, in the case of a serious failure such as a failure of the main transmission line or the head entry modulator for the main transmission line, the downlink signal sensor switches the changeover switch and activates the head end remodulator for the backup transmission line. However, information communication is maintained only through the backup transmission line. [Effects of the Invention] As described above, according to the present invention, in the event of a partial failure, such as a failure of a modem at one station or an abnormality in a branch terminal, only the relevant part is affected. It can be switched to the backup system. The only station using the backup system is the failed station, and only the station related to the failed modem switches to the backup system, and the other stations are in the same state as normal, so there is no abnormality. It is possible to guarantee the same reliable data transmission as before the occurrence of this problem.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional duplex bus type network. In the figure, 3A, 3B, 3C are stations, 4
A, 4 B, 4C are switching devices, 5 is a bidirectional amplifier for coordination, 6 is a downstream signal sensor, 7 is a changeover switch, 10 is a main transmission line, 1 1A, 1 18.1 IC is a main modem, 12 is the main system termination resistor, 13 is the main system brancher, 14 is the main system bidirectional amplifier, 15 is the main system transmission line head entry modulator, 20 is the protection system transmission line, 2 LA, 2 18.2 1C is the protection system modem, 23
22 is a standby system P end resistor, 24 is a standby system bidirectional amplifier, and 25 is a standby system head end remote modulator.

Claims (1)

[Scope of Claims] 1. In a broadband bus-type network in which a transmission path is provided with branch sections at a plurality of locations and stations are connected to each branch section, and data is transmitted to each other via the transmission path, a data input/output section of each station is provided. The modem section is duplicated, each modem is connected to two different transmission lines, the first head entry modulator is connected to one end of one system, and the other end of the system is connected to a terminating resistor at one end. A second head entry modulator is switchably connected to the other end of the terminated other system via a changeover switch, and only the corresponding station is switched to the other system in the event of a local failure of a modem or the like. A redundant system for bus-type networks. 2. The bus type network duplication system according to claim 1, further comprising a relay transmission device provided between the other end of said one system and said changeover switch.